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Flashcards in Prosthodontics Deck (243):
1

mechanical properties of resins are influenced by

1. MW of the polymer
2. degree of cross-linking
3. composition of monomers
4. EXPAND in water and distort when dried out

2

acrylic resin powder (polymer) is made of

polymethyl methacrylate (PMMA) polymer, benzoyl peroxide initiator
-cross linking contributes to strength

3

acrylic resin liquid (monomer) is made of

PURE methyl methacrylate (MMA) monomer, hydroquinone inhibitor, cross-linking agents, checmical activator (dimethyl-p-toluidine)

-other monomers like ethyl methacrylate are less irritating to the pulp

4

heat is used as an accelerator to decompose ___ (initiator) into free radicals to initiate polymerization of MMA PMMA

benzoyl peroxide

5

the liquid monomer most frequenly used in polymer systems in dentistry

MMA

6

heat cured resins have more/less residual monomer and higher MW than self-cured resins

LESS, so they are stronger and have better color

7

in self-cured materials, a chemical activator like __ (tertiary armine) is added to the monomer MMA to decompose the benzoyl peroxide into free radicals -> polymerization

dimethyl-p-toluidine

8

what kind of resins are used for repairs

self-cured (instead of heat) because risk of distorting the denture is less

9

denture STABILITY involves

-relationship of denture base to bone that resists DISLODGEMENT in horizontal direction
-resistance to horizontal, lateral, torsional forces

10

denture SUPPORT involves

resistance to VERTICAL seating provided by rests and the denture base

MOST important design characteristic for oral health

11

denture RETENTION involves

resisting force to gravity, sticky foods, forces assoc. with mandibular movement
-direct and indirect retainers, clasps in undercuts provide retention

12

denture RECIPROCATION involves

part of restoration counters effects in another
ex. lingual clasp arm counteracts buccal arm
-achieved by opposing flexible retainers with guide planes, minor connectors, rigid clasp arms, plating

13

bracing is

horizontal force ransmission by placing rigid parts of clasps or other parts in non-undercut areas of abutment teeth

14

guidance is

during insertion and removal, obtained by contact of rigid parts of framework with areas on axial tooth surfaces parallel to path of insertion

15

impression taking for complete dentures recommend

-border molding
-best for pt with loose hyperplastic tissue is to register it in a PASSIVE position

16

primary indicator of accuracy of border molding is

stability and lack of displacement of custom tray in mouth

17

most critical area in border molding for max denture is the

mucogingival fold above the maxillary tuberosity
-important for retention
-other areas: labial frena in midline and bicuspid area

18

in border molding, the distofacial extension is determined by position and action of the __ muscle

distolingual is limited by action of the __ muscle

MASSETER (anterior fibers pass outside buccinator)
-the buccinator lies under the flange in this area but the fibers run anteroposterior in a horizontal plane and their action is weak

SUPERIOR CONSTRICTOR

19

most likely tissue rxn to gross overextension is

epulis fissuratum
-due to clefts found in hyperplastic tissue
-occurs in vestibular mucosa
-appears as PAINLESS FOLDS of fibrous tissue

20

localized or generalized chronic inflammation. trauma and secondary fungal infection are the most likely causes

denture stomatitis

tx: better OH, rest, anti-fungal (Nystatin)

21

condition frequently observed under ill-fitting denture, esp. with a relief chamber, masses are painless, firm, pink or red nodular proliferations, candida albicans may contribute

inflammatory papillary hyperplasia

22

masseter's superficial layer originates from the maxilla's __ and inserts in the mandible where?

maxilla's zygomatic process and inserts at the angle and lower lateral side of the ramus of the mandible

23

a tendon that lies btw the buccinator and superior constrictor is the

pterygomandibular raphe

24

a thin, curved bony process extension of the medial pterygoid plate of sphenoid bone that serves as the superior attachment of the pterygomandibular raphe

hamulus

25

thin cleft btw maixllary tuberosity and hamulus, where a max denture must extend into is the __ __

hamular notch

26

group of mucous gland ducts, posterior to jxn of hard and soft palates near midline is

fovea palatini

27

palatoglossus, superior pharyngeal constrictor, mylohyoid and genioglossus are influential in border molding what area?

LINGUAL of mandibular impression

28

difference btw border molding with ZOE instead of modeling plastic is that

ZOE has to be border molded in one insertion and within setting time

29

what regulates the paths of the condyles in mandibular movements?

size and shape of bony fossae and menisci and muscles

30

primary support for max denture are

1. residual ridges
2. palatal rugae

31

if pt complains that when they smile, upper denture doesn't hold, you need to adjust

buccal notch and buccal flange due to excessive thickness

32

if pt complains that max denture is loose when mouth is wide open, might be because

maxillary DB flange being too thick can interfere with movement of the coronoid process

33

if pt has sore gums and aching muscles at bottom of face after wearing dentures for hours it means

opposing teeth of denture have enough space -> reduce VDO

34

tingling or numbing at corner of mouth or lower lip after few days is caused by

excessive pressure from lower buccal flange in region of mental foramen

35

posterior palatal seal in max complete denture

-excessive depth usually causes unseating of the denture
-always done by the DENTIST
-width of seal AP is concave, 3 mm in midline and 6 mm in lateral areas

Functions
1. completes border seal
2. prevents food impaction
3. improves retention
4.** compensates for polymerization and cooling shrinkage of denture resin during processing

36

posterior palatal seal landmarks

posterior outline - vibrating line, the hamular notch is ON the posterior border

anterior outline - formed by "blow" valsalva line at distal extent of hard palate, approximation of the jxn of hard and soft palate

37

changes on max arch in pt who wears complete max denture and LACKS posterior occlusion includes

-hyperplastic tissue on anterior max ridge
-poor bone structure
-fibrous tuberosities
-pt's CC: loose denture, can't see upper teeth

38

pt with upper complete and mand bilateral distal extension may show

decreased VDO, prognathic appearance

39

when a complete max denture opposes natural mand. anterior teeth, what happens to the max anterior ridge?

becomes FLABBY

40

when the posterior max buccal space is entirely filled with the denture flange, interference may occcur with movement of the

coronoid process -> dislodgement

41

max. sinus enlarges throughout life if it's not restricted by teeth or dentures. as it enlarges, what happens to the tuberosity?

moves downward
-if there is no contact with the retromolar pad at VDO, the tuberosity must be reduced

42

submucosal vestibuloplasty

usually on upper arch to improve denture base area

43

palatal tori occur in __ % of population and are more common in males/females?

20-25%, women
-tissues covering it are thin with poor blood supply, post-op healing is slow
-NOT usually removed for denture fab but MANDIBULAR ones are!

44

indications for palatal tori removal include

impinging on soft tissue, fills vault and prevents formation of adequate denture base, undercut, extends so far posterior that it interferes with posterior palatal seal, psychologically disturbing to the pt

45

primary support area for mandibular complete denture is

BUCCAL SHELF (bone structure, right angle to occlusal plane)
-if residual ridges are large and broad then it's also support

46

second peripheral seal for mand. coimplete denture is the __ border

anterior lingual

47

what will happen to the alveolar ridge is a mand. complete denture base terminates short of the retromolar pad?

RESORPTION of the alveolar ridge

48

underlying __ __ under the retromolar pad resists resorption

basal bone

49

mand. dentures don't rely on suction, but rely on STABILITY from

covering as much basal bone as possible without impinging on muscle attachments

50

mandibular molars should NOT be placed over ascending area of the mandible because

the occlusal forces over the inclined ramus dislodge the denture

51

most common cause of POROSITIES in a denture is from

insufficient pressure on the flask during processing

-acrylic resin for repairs should be under 20-30 psi air pressure
-usually happens in THICKEST part of the denture
-also occur if packing and processing of powder and liquid is too plastic (stringy/sandy)

52

purpose of occlusal rims is to

determine and establish VDO
make jaw relation records
establish and locate future position of teeth

53

in a complete denture pt, when the teeth, rims and central bearing point are in contact and mandible in CR, then the length of the __ is the occlusal vertical dimension

length of the face

54

correct VDO is evaluated using 4 methods

1. appearance of facial support
2. observation of space btw rims at rest
3. measurement btw dots on face
4. observation when S sound is enunciated, check speaking space

55

excessive VDO can result in

trauma to underlying supporting tissues

56

__ is the most likely cause of cheilosis

closed vertical dimension

57

what has the greatest effect on setting of mandibular 2nd molars?

posterior determinants of occlusion (2/3 height of retromolar pads)

58

frankfort horizontal plane extends from

outer canthus of eye to ear tragus

59

what 3 factors affect correct positioning of the lips in complete dentures

1. VDO
2. thickness of anterior border
3. teeth position

60

changes assoc. with the edentulous state

-deepening of nasolabial groove and narrowing of lips
-prognathic appearance, increase in columella-philtral angle
-loss of labiodental angle and decrease in horizontal labial angle

61

after first few days of new dentures, pt should expect some difficult in masticating most foods and excess saliva cause of

reflex parasympathetic stimulation of salivary glands

62

2-step schedule for tooth removal prior to delivery of immediate completes

step 1 - ext all posterior teeth except max 1st PM and opposing tooth (a stop to keep VDO)

step 2 - after ridges heal, anterior teeth are ext at time of insertion

63

1st day of wearing immediates instructions

not to remove denture
eat soft foods
return in 24 hrs for eval

64

primary role of anterior teeth is

esthetics

most common error is placing teeth directly over the edentulous ridge

labial surface of central incisor should be 8 mm anterior to the incisive papilla

65

BL width on denture teeth are more narrow to

reduce stress transferred to denture support area while eating, and increases tongue space

66

common errors when arranging denture teeth

-set mand teeth too far forward to meet max teeth
-fail to make canines turning point of arch
-set mand 1st PM buccal to canines
-establish occlusal plane arbitrarily
0not rotating anterior teeth enough to give narrower effect

67

why do you use plastic instead of porcelain teeth

plastic bonds well to acrylic resin

68

immediate dentures should be relined when?

in 5 and 10 months post-ext

69

a flabby max anterior ridge under a complete denture is often assoc. with

retained natural mandibular anteriors

70

benefit of an overdenture (root-retained) is

PRESERVATION of the ALVEOLAR RIDGE

71

potential probs with new dentures

1. cheek biting caused by
-posterior teeth set edge-edge, need proper horizontal overlap
-inadequate VDO
-bite corners of mouth -> reset canines and PMs

2. lip biting - caused by reduced muscle tone or overbite

3. tongue biting - posterior teeth too far lingual

4. speech - bad tooth position, palatal contours

72

pt edentulous for many yrs has more distorted speech than pt edentulous for a short time due to

loss of tonus of tongue muscles

73

what might you see in an uncontrolled diabetic

impaired healing
poor tissue tolerance
rapid bone resorption

74

Sounds

1. S - bring mandible close to maxilla
2. hissing - incisal edges almost touching
3. Th - tongue protrudes 2-4 mm btw max and mand teeth
4. F and V - incisals of max and lower lip
5. P and B - lips
6. T - if teeth are too lingual it will sound like a D and vice versa
7. whistling - from high palatal vault or constricted palate, insufficient overjet, overbite, bad palatal contour

75

if pt complains of irritation of basal seat, can be cause of

premature occlusal contacts (most common cause!)
bad OH
nutrition imbalance
excessive VDO

76

pt with max denture complains of burning sensation means

pressure on INCISIVE FORAMEN

in mandibular anterior -> MENTAL FORAMEN

77

facebow records

pt's maxilla/hinge axis relationship
-orients maxillary cast to hinge axis on articulator
-hinge axis facebow enables dentist to alter VDO on articulator

78

pantograph is used for

tracing paths of the condyle, uses 2 facebows

79

preferred method to preserve facebow transfer is a __ index

plastic index

2 methods
1. plaster index of max denture before removing denture from articulator and cast
2. place a piece of 10x wax on occlusal of mandibular and close the articulator in CR, chill, drop incisal guide pin to touch the table

80

ARCON articulator

condyle on LOWER member
condylar paths on UPPER

angle btw condylar inclination and occlusal plane is FIXED
-used for dx mounting of study casts

81

NON-ARCON articulator

condyle on UPPER member
condylar paths on LOWER

angle btw condylar inclination and occlusal plane is NOT fixed
-more proper to fabricate DENTURES

82

diabetes is assoc. with

delayed healing
rapidly progressing perio disease with bone loss
increased calculus
predilection for periapical abscesses

83

can surveying determine areas of support?

no

84

kennedy classifications are based on

the most posterior edentulous area to be restored

85

4 Kennedy Classes

I - bilateral distal extension
II - unilateral distal extension
III - unilateral edentulous spaces bound by teeth, tooth-borne
IV - anterior teeth missing and across midline

86

Craddock Classification is based on the denture type

Type I - mucosa borne
Type II - tooth borne
Type III - mucosa and tooth borne

87

major connector

connects parts of the prosthesis located on one side of the arch to the other
-must be RIGID
-should be free of movable tissues and shouldn't impinge on gingiva
-relief should be provided
-bony and soft tissue prominences should be avoided

88

major connectors most frequently encounter interferences with what teeth

lingually inclined mandibular premolars

89

mandibular major connectors
1. lingual bar
2. lingual plate
3. labial bar

1. lingual bar - upper border at least 4 mm below gingiva
2. lingual plate - upper border should be at middle 1/3 of lingual surface
3. lingual bar - 3 mm below gingiva

90

maxillary (palatal) major connectors
1. transpalatal bar
2. horseshoe
3. AP bar
4. palatal plate connector

1. palatal bar - lack rigidity, for toothborne, short span
2. horseshoe - for torus
3. AP bar - MOST RIGID
4. palatal plate connector - for simple edentulous areas and full palatal coverage

91

distal extension RPD receives support from

residual ridge, tissue-bearing areas, selected abutment teeth, fibrous CT over alveolar process

92

most important factor in determining success of distal extension RPDs is

proper coverage over residual ridge
-should go over retromolar pad for stability and minimizing torque

93

if pt complains of sensitivity to percussion on abutment tooth of distal extension RPD, prob is most likely

OCCLUSION
-defective occlusal contacts can also cause a feeling of "looseness"

94

altered cast technique purpose

record form of edentulous segment without tissue displacement and to accurately relate edentulous segment of teeth via metal framework

impression materials can't record anatomic form of teeth and physiologic form of soft tissue in a functional relationship simultaneously

95

stress breaker

device that relieves abutment teeth to which FPD or RPD is attached, of all or part of forces generated by occlusal function

96

when a stress breaker is incorporated next to a free-end distal extension RPD, the functional stress is directed onto the

residual ridge, and only minimal transfer of functional stress to abutment teeth occurs

97

3 types of stress breakers
1. wrought-wire clasp
2. split-bar major connector
3. stress-breakers with movable joint

1. wrought wire - simplest form, higher yield strength, flexible, ductile, resilient, greater tensile strength
2. split bar (Ticonium 'hidden-lock') - flexible btw direct retainer and denture base
3. with movable joint - btw direct retainer and denture base (DE hinge, dalbo attachment, Crismani attachment, ASC-52 attachment)

98

cast metal is

any metal melted and cast into a mold
-when the casting is cold-worked ex. wire, it's a "wrought metal" (tensile strength, hardness, strength > cast)

99

elongation is

the most important mechanical property involved when a base metal RPD clasp is adjusted

100

cast wire compared to wrought wire

less yield strength, less flexibility, less ductility and resilience
-cast wire has unavoidable POROSITIES

101

indirect retainers include

rests, minor connectors, proximal plates
-fxn to prevent/counteract vertical dislodgement of distal extension base of RPD
-ANTI-ROTATIONAL
-counteracts upward rotation of base and serves as a 3rd reference for seating the framework and making altered cast impressions
-protects soft tissues

102

minor connector

connects major connector or base of RPD with other units (clasps, indirect retainers, occlusal rests)

2 functions
1. transfer functional stress to abutment teeth
2. transfer effect of retainers, rests, stabilizing components

103

indirect retainer design

-should be at right angles to fulcrum line
-IR should be in rest seats
-IR located farthest from clasp tips closets to edentulous areas provides best leverage against lifting/dislodging

104

rests are to provide

1. occlusal
2. cingulum
3. incisal

VERTICAL support for RPD

1. occlusal - forms acute angles with minor connectors, thickness 1.5 mm
2. cingulum - usually confined to maxillary canines, sometimes max centrals
3. incisal - not esthetic

105

direct retainers
1. intracoronal attachment
2. clasps (extracoronal retainers)

1. intracoronal - most esthetic!

2. clasps - most common, 2 types

106

2 types of clasps
1. Suprabulge
2. Infrabulge

1. suprabulge - originate from ABOVE survey line
-circumferential
-ring clasp: encircles nearly all of tooth to engage an undercut on same side of tooth as the rest
-embrasure clasp: when no edentulous space
-reverse action clasp (hairpin): engage undercut on same side of abutment as the rest or any posterior tooth
-extended arm: circumferential that extends to increase splinting and get better undercut
-1/2 and 1/2 clasp: one circumferential from rest and another from minor connector on opposite side

2. Infrabulge (Roach, I, J, U, L, T bar) - approaches crown from below height of contour, must not be placed in tissue undercuts

107

pros/cons of infrabulge retainers

pros - efficient retention, less distortion of coronal contours, cleaner, esthetic, adjustable

cons - irritating to vestibule, not good for bracing

108

infrabulge retainers provide retention by

resistance of metal to DEFORMATION (rather than frictional resistance by contact of clasp to tooth)

109

intracoronal retainers

produce mechanical and frictional retention, esthetic, not used for distal extension

110

short arm clasp < 7 mm should be made in a __ gauge wire

20 gauge, need finer gauge for flexibility

111

flexibility of a retentive clasp depends on

1. clasp length
2. thickness
3. width
4. cross-sectional form
5. clasp taper
6. clasp material

112

failure of RPDs due to clasp design is best avoided by

altering tooth contours

113

reciprocating element must be placed __ the direct retainer, and contact the abutment where?

OPPOSITE
-must contact abutment as the retentive tip passes over the tooth's height of contour

114

clasp assembly consists of

retentive clasp arm, reciprocal (stabilizing clasp arm), minor connectors/rests

115

reciprocal clasp arm functions on RPD include

reciprocation, staiblization, indirect retention (bracing)

116

facial and proximal contours of __ and __ most often need to be altered

premolars and molars

117

guiding planes serve to assure

predictable clasp retention

118

precision attachment restoration

metal male and female parts that fit together

semi-precision attachment - cast into the crown and RPD

con - NEVER in distal extension RPD without stress breaker

119

base metal alloys

compared to gold: lower density, higher resistance to deflection, higher modulus of elasticity, higher melting point temp, lower yield strength

120

advantages of rpd cast chromium cobalt alloys

corrosion resistant, high strength, low specific gravity, low density, high modulus of elasticity (stiffness), cheap

BUT very inflexible (no ductility or malleability)

121

chromium responsible for

cobalt is for

nickel?

corrosion resistance
-RPD is resistant to tarnish and corrosion cause of its surface oxide layer

cobalt - incr. rigidity, strength

nickel - ductility

122

ADA Classes of Alloys (I-IV)

I: small inlays
II: larger inlays and onlays
III: onlays, crowns, short-span FPDs
IV: thin veneer crowns, long-span FPDs and RPDs

123

elongated grains in wrought wire indicates it has been

cold worked

124

Paget's Disease (osteitis deformans) often discovered in dental office cause

pt's dentures don't fit due to widening of alveolar ridges
-a chronic bone disorder, bones enlarge and are deformed
-enlarged head, hearing loss, blindness

125

__ is the most common change assoc. with systemic disease

osteoporosis

126

veneers should be treated with

-silane, protected with light cured unfilled resin
-etch tooh and apply unfilled bond resin
-composite applied on veneer
-stick on veneer

127

a reverse 3/4 crown is most often made for what tooth

mandibular molar

128

7/8 crown is

3/4 crown with vertical distobuccal margin positioned slightly mesial to the middl of the buccal surface
-good esthetics, good abutment

129

bevel (feather-edge) margin

best for CAST FULL GOLD but in practice it's hard to read on impression and die

least marginal strength

-> an ACUTE edge/angle is the optimum margin for casting

130

chamfer margin

PREFERRED FINISHING LINE for cast full gold
-adv of easily definable margin and minimal tooth prep

131

shoulder margin (BUTT)

for porcelain jacket and ALL CERAMIC
-edge strength of porcelain is low
-provides resistance to occlusal forces and minimizes stress
-disadvantage is inaccuracies in crown fit are reproduced at margin -> incr. thickness of cement
-POOREST for cast metal

132

shoulder with bevel

allows sliding fit
-for proximal box of inlays and occlusal shoulder of mand 3/4 crowns, labial margins of PFMs

133

most common cause of crown failure is

lack of attention to tooth shape, position, contacts

134

greatest potential for wear exists btw what 2 materials

porcelain and tooth
-gold is better for occlusal cause its wear is more like enamel
-porcelain wears opposing dentition faster
-gold preferred for bruxism

135

FULL GOLD CROWNS

circumferential and occlusal reduction 0.5-1.0 mm

136

ALL-CERAMIC CROWNS

tendency to fracture at minimum deformation
-LOW FLEXURAL STRENGTH

137

rank porcelain flexural strengths

1. in-ceram zirconia = 800 Mpa
2. procera
3. in-ceram
4. IPS empress
5. aluminous = 100
6. feldspathic = 60-90

138

preps for what restorations must be well rounded with no sharp angles

all-ceramic

139

porcelain is much stronger under __ forces than tensile forces from opposing teeth

compressive

140

CAD-CAM

ceramics processed via a computer controlled milling machine

141

porcelain layers - restoration is bulked out to compensate for 20% shrinkage

1. opaque
2. body
3. incisal

1. opaque - mask color of the metal
2. body - makes up bulk and color shade
3. incisal - translucent to incisal or cuspal 1/3

142

metamerism

phenomenon that causes teeth/porcelain to appear color matched under one light, but different under another
-staining porcelain decreases value and increases metamerism
-light source must contain wavelength of the color matched to see that color

143

fluorescence

optical property by which a material (teeth) reflects UV radiation
-contributes to brightness and vital appearance

human teeth fluoresce BLUE-WHITE (400-450 nm)

blue fatigue accelerates yellow sensitivity

144

color of a pigment is determined by

selective absorption and selective radiation

145

SHADE is matched on the color's
1. value
2. chroma
3. hue

1. value - color's brightness, almost impossible to increase value

2. chroma - saturation, most important in shade matching

3. hue - color families, orange is most often used

146

dental porcelain is a mixture of

feldspar*, quartz, metallic oxides

COMPRESSIVE strength > tensile or shear strengths

BRITTLE

147

3 classes of dental porcelains
1. high fusing
2. medium fusing
3. low fusing

1. high - DENTURE teeth
2. medium - all ceramic and porcelain jacket
3. low - PFM
-aluminum oxide to increase resistance to "slumping"
-calcium oxide
-other oxides to reduce cross linking to lower fusing temp

148

degassing (heat tx)

casting is heated in a porcelain furance to 980C to burn off impurities before adding porcelain
-too low of temp will form bubbles

149

causes of porcelain fracture at porcelain metal interface

main cause - bad metal framework design

also: degass at low temp ,contamination, fuse opaque coat too low temp

150

metal and ceramic must have closely matched

coefficients of thermal expansion (alloy usually harder) to avoid TENSILE stresses at PFM interface

151

alloys should have a high __ and high __ to reduce stress on porcelain

proportional limit

high modulus of elasticity

152

types of composition all ceramic crowns

feldspathic porcelain - conventional porcelain jacket
aluminous porcelain - to reinforce glass [Inceram]
mica glass - [Dicor, Cerapearl]
crystalline-reinforced glass - leucite added [Empress]

153

types of fabrication method all-ceramic crowns

refractory die technique - Inceram
casting - Dicor
press - Empress

154

3 stages in firing dental porcelain

1. low bisque
2. medium
3. high

155

glazed porcelain is

non-porous, resists abrasion, esthetic, well tolerated by gingiva

156

PFMs requirements

porcelain 0.7 mm
metal coping 0.3-0.5 mm for high noble gold
(base metal alloys 0.2 mm)

need space for 1.5 mm, supporting cusps require 2.0 mm reduction -> ideal is 1.5-2.0 mm (labial is 1.5)

opposing walls converge < 10 deg

157

how do PFM and all ceramic compare in tooth reduction

SAME

1.5-2.0 mm

158

metal coping (substructure) must have all of its surfaces __ to prevent porcelain shrinkage

metal coping ensures __ and maximizes strength of the porcelain veneer

smooth and round

proper crown fit and maximizes strength of porcelain veneer

159

outer jxn of porcelain to metal should be at what angle

90 deg
to avoid burnishing the metal and prevent subsequent porcelain fracture

160

3 kinds of PFM alloys

1. high gold noble alloys - 98% gold, platinum, palladium, don't oxidize on casting, BEST

2. palladium-silver: oxidizes on casting

3. nickel-chromium: readily oxidizes

161

sprue diameter should be

equal or greater than the thickest portion of wax or plastic

162

gypsum bonded investments

for GOLD alloys
strength depends on amt of gypsum

CAN'T be used for titanium crowns/copings, Type IV gold alloys, susbstructure for PFMs

163

phosphate bonded investments

base metal alloys for PFMs

casting temp > 2100 F (1150 C)

164

silica bonded investments

base metal alloys for RPDs

mag phosphate + ammonium phosphate for room temp.

higher temps, SILICOPHOSPHATES give it strength

165

quartz or cristobalite

refractory materials to provide thermal expansion

166

4 mechanisms to compensate for solidification shrinkage of alloy during casting

1. setting expansion - crystal growth, restricted by metal investment ring

2. hygroscopic expansion - let investment set in water

3. thermal expansion - when it's heated in burnout oven

4. wax pattern expansion - wax pattern warmed while investment is still fluid

167

porcelain adheres to metal primarily by

CHEMICAL BOND

silicon dioxide and metal alloy

168

cements do NOT increase crown retention, apply cement to both restoration and the tooth, 3 types

1. composite resin - for CERAMIC crown, STRONGEST bond, after etching tooth

2. zinc phosphate - can be used for ceramics, good compressive strength, high pH so must use varnish!

3. zinc polycarboxylate or ZOE - bio compatible, better resistance to solubility than zinc phosphate, adhere to calcified dental tissue

169

occlusion of gold restorations is best checked with

silver plastic shim stock

170

radiographic signs of occlusal trauma

hypercementosis, root resorption, alteration of lamina dura, wide PDL space (NOT pockets)

171

non-rigid connector

key and keyway, SHORT-SPAN bridge replacing one tooth

indicated when retainers can't be prepared to draw together without excessive tooth rdxn

T-shaped most common

path of insertion of key into keyway should be parallel to path of the RETAINER

solder joints

172

replacing how many teeth is the max?

3 teeth, under ideal conditions

173

most likely indication for tooth splinting is

tooth mobility with pt discomfort

174

can you splint natural teeth and implants in a FPD?

controversial, DON'T

175

types of pontics (3)

1. modified ridge lap - esthetic zones, all convex surfaces for easy cleaning

2. sanitary - space btw pontic and ridge, not esthetic, conical pontic for thin ridge

3. saddle - looks most like tooth, covers ridge, hard to clean and NOT used! ovate pontic is a sanitary substitute

176

pontic should be convex/concave M-D? touch the ridge? be convex/concave F-L?

CONVEX M-D
touch residual ridge (passive pinpoint)
CONCAVE F-L

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quenching

metal is rapidly cooled, to maintain mechanical properties assoc. with crystalline structure

to achieve a softened condition for Type III dental gold alloy, quench in 30-40 sec

advantages - noble metal alloy is left in an annealed condition, casting is more easily cleaned

178

burnishing

related to polishing, surface is drawn or moved

179

annealing (degassing)

soften metal by controlled heat and cooling

to make the metal TOUGHER and LESS BRITTLE

gold foil is annealed to remove volatiles prior to placement in cavity

180

fritting

manufacturing low and medium fusing porcelains

181

soldering

join 2 metals using a filler material or solder

gold - fixed bridges
silver - ortho

CLEANLINESS is most important prereq of soldering, cause it depends on WETTING surfaces to achieve bonding, flux displaces gases and removes corrosion products

182

fluxing

oxidative cleaning of area to be soldered
-potassium fluoride - agent most commonly added (steel or cobalt chromium alloys)

anti-flux: outline the area, soft graphite pencil

183

pickling

heat casting then place in acidic solution -> can warp! or you can place it in solution then heat it

50% HCl

removes surface oxide film on gold castings

184

cold work (strain hardening or work hardening)

HARDENING (deformation) of metal at room temp ex. bend a wire

-polycrystalline metal, defects build up at grain boundaries
-result of strain hardening with increase in cold work is FRACTURE

surface hardness, strength, proportional limit are INCREASED while ductility and resistance are DECREASED

185

SLIP

deformation process, simultaneous displacement of entire plane of atoms relative to plane and below plane

186

electrosurgery objectives

indications

contraindications

obj - coagulation, hemostasis, access to cavosurface margins, reduce inner wall of gingival sulcus

indications - remove hyperplastic tissue, in place of gingival retraction cord, for crown lengthening

contraindications - thin attached gingiva, dehiscence suspected, NOT pts with cardiac pacemakers

187

temperomandibular joint is?

lower and upper compartment contain

combined HINGE and GLIDING joint (ginglymoarthrodial joint)

lower (condyle-disc) compartment: HINGE (rotary), only in CR

upper (mandibular fossa-disc) compartment: SLIDING (translation), when lateral pterygoids contract simultaneously, discs and condyles slide forward down over articular eminence

188

muscle groups acting on TMJ include (3)

1. elevator muscles (CLOSE) - masseter, medial pterygoid, temporalis (anterior fibers)

2. depressor muscles (OPEN) - lateral pterygoid, anterior belly of digastric, omohyoid

3. protrusion - lateral pterygoids

189

centric relation (retruded contact position)

-ligament guided, supero-anterior position of condyle along articular eminence of condyle with articular disc interposed btw condyle and eminence

most unstrained, retruded anatomic and functional position of mandibular condyle heads in the glenoid fossae

a BONE-to-BONE relationship independent of tooth contact

closing end point of the retruded border movement

190

centric occlusion (intercuspal position)

TOOTH-guided position, MI, during typical swallowing
-masseters contract and tongue tip touches roof of mouth
-tooth contacts are longer in swallowing than chewing

191

freeway space

2-6 mm, mandible at rest
-tonic stretch reflex of mandibular elevator muscles
-muscle guided position

192

vertical dimension of occlusion (VDO)

vertical length of face as measured btw 2 arbitrary points when teeth are in CR
-verify by phonetics
-excessive VDO causes CLICKING of denture teeth (also lack of retention can cause clicking)
-decreased VDO often results in cheek biting

193

vertical dimension of rest (VDR)

length of face measured btw 2 points when mandible is in rest

VDR = VDO + interocclusal difference

194

condylar guidance

-totally dictated by patient
-inclination depends on: shape and size of bony contour, action of muscles, limiting effects of ligaments

195

what record is the least reproducible maxillomandibular record?

protrusive record

196

retrusive movement requires condyles to move

backward, upward

197

in lateral movements, working condyle moves ___, non-working condyles move __

working - down, forward, laterally
non-working - down, forward, medially

198

what factor is the most important aspect of condylar guidance that affects the selection of posterior teeth with appropriate cusp height?

inclination of condylar path during protrusive movement

199

in complete dentures, the condyle path during free mandibular movements is governed mainly by the

shape of the fossa and meniscus (articular disc) and muscular influence

200

4 dentition features that directly effect PDL health & hard tissue anchorage to resist occlusal force

1. anterior teeth have slight or no contact in MI
2. occlusal table < 60% of F-L width
3. occlusal table at right angles to long axis
4. tooth position in arch

201

jaw relation most used in actual design of restorations is

ACQUIRED centric occlusion

202

compensating curve

anteroposterior and lateral curve
-under the DENTIST'S control
-helps balanced occlusion

203

5 factors that govern balanced articulation

1. inclination of condylar guidance
2. " of incisal guidance (horizontal and vertical overlap)
3. " of occlusal plane (plane of orientation)
4. convexities of compensating curve
5. angle and height of cusps

204

bilateral eccentric occlusion

NOT for RPDs unless the it opposes a complete denture

205

group function occlusion (unilateral balanced)

NO non-working side contacts in natural dentition, only working side

206

purpose of protrusive record

register condylar path, adjust condylr guides of articulator

207

protrusive movement, mandible can protrude __ mm

how do the condyles move

10

condyles move DOWN and FORWARD

208

how do you correct centric interference (forward slide)

grind MESIAL inclines of maxillary teeth and DISTAL inclines of mandibular

209

mutually protected "canine guided" occlusion

anterior teeth protect posteriors in all mandibular excursions
-vertical overlap of max and mand canines cause disculsion of ALL posterior teeth when mandible moves to either side

210

anterior guidance (coupling)

result of horizontal and vertical overlap of anterior teeth, produce disclusion of posteriors

the greater the overlap, the longer the cusp height

211

incisal guidance

second end-controlling factor in articular movement, influenced by esthetics, phonetics, ridge relations, arch space, inter-ridge space

212

these are end-controlling factors

incisal guidance

right and left condylar mechanisms

213

supporting cusps (stam or centric cusps)

characteristics

more robust, suited to crush food

characteristics
1. contact opposing tooth in intercuspal position
2. support vertical dimension of face
3. closer to F-L center of tooth
4. outer incline has potential for contact
5. broader, more round cusp ridges

214

non-supporting cusps (guiding or shearing)

maxillary buccal cusps
mandibular lingual cusps

have narrower and sharper cusp ridges

inner occlusal inclines leading to guiding cusps are guiding inclines

215

selective grinding in complete dentures in centric relation (CR)

what cusps can you grind and not grind?

primary centric holding cusps are - Max lingual cusps (NEVER GRIND)

secondary centric holding cusps are - Mand. buccal cusps ONLY grind if there is a balancing (non-working) side interference

only grind BULL cusps!

216

functionally generated pathway technique

allows cuspal movements of the dentition to be recorded in wax intra-orally then transferred to articulator in the form of a static plastic cast (functional index)

all mandibular motion must be directed from an ECCENTRIC centric position

217

in ideal intercuspation,

ML cusps of permanent mandibular molars occlude with __

buccal cusp tips of permanent maxillary premolars oppose __

1. LINGUAL embrasure between their counterpart and the tooth MESIAL to it

2. FACIAL embrasure between their counterpart and the tooth DISTAL to it

218

which maxillary cusps and mandibular cusps are GUIDING cusps?

maxillary buccal cusps

mandibular lingual cusps

guiding = guide away from midline

219

BENNETT movement

lateral transition (sideshift) of WORKING condyle during lateral excursions
-also called lateral shift or immediate side shift
-influences the MESIODISTAL position of the posterior teeth cusps

220

translation in mandibular opening occurs in lower/upper compartment of TMJ?

UPPER

221

what are the muscles involved in closing (elevating) the mouth to centric

medial pterygoid
masseter
temporalis

222

what kind of load is the most destructive on the periodontium?

horizontal

223

bite registration material should

offer minimum resistance to pt's jaw closure and have LOW FLOW at mixing

addition-reaction silicone materials

224

2 types of polymerization in impression materials

1. addition - formation of polymer without forming any other chemical
2. condensation - when chemicals or byproducts are produced that are not part of the polymer

225

hydrocolloids have the advantage of __

wetting intraoral surfaces BUT have limited dimensional stability

226

reversible hydrocolloid (agar-agar)

physical state can be changed from a GEL SOL by applying heat and is reversed back by removing heat

pros - easy to pour, no mixing req, no costum tray, good shelf life (1-2 yrs), cheap

cons - must be poured immediately, finish line difficult to read

227

irreversible hydrocolloid (alginate)

very limited dimensional stability

cons - unstable, fragile, must be poured immediately

sodium phosphate controls setting time (retarder)

FAST removal of impression from mouth increases the compressive and tear strength

228

alginate sets via a chemical rxn

double decomposition rxn

calcium sulfate + potassium alginate

229

gelation

setting process of alginate

-higher temp = shorter gelation time (sets faster)
-calcium sulfate "reactor"
-inaccuracies can be caused by fracture of fibrils
-SYNERESIS (shrinkage in alginate)

230

elastomers are?

4 types

NON-AQEOUS polymer based rubber impression materials with good elasticity

1. polysulfides
2. silicones
3. polyvinyl siloxanes
4. polyethers

231

Polysulfides (rubber base, mercaptan, thiokol)

base of liquid polysulfide polymer and accelerator of lead dioxide (brown, stinky).

-requires custom tray
-sets in 12-14 min (LONGEST set time)
-18 mo. shelf life
-need occlusal stops
-good flow, high flexibility, good tear strength

232

Silicones (condensation or convention)

base is liquid silicone polymer (dimethyl siloxane) and reactor a cross-linking agent (ethyl ortho-silicate) and activator (tin octoate)

-evaporation of alcohol causes shrinkage of material and resultant poor dimensional stability

cons - custom tray req, low tear strength, pour shortly after removal, hydroPHOBIC, medium stiffness
-long setting time 6-10 min.
-"putty/reline" form allowing delayed pouring up to 6 hrs.

233

Polyvinyl Siloxanes (additional silicones or vinyl polysiloxanes)

upon mixing there's an addition of silane hydrogen groups, PVS can be poured up to 1 week
-don't wear latex! sulfur retards the setting
-moderate set time 6-8 min.
-very good dimensional stability and low permanent deformation
-poor tear strength, high stiffness, temp sensitive

most widely used, most accurate! less polymerization shrinkage, low distortion, can be poured up to 1 week

234

Polyethers (Impregnum/Premier & Polygel (Caulk))

rubber base has polyether, accelerator has cross linking agent (aromatic sulfonic acid ester)

pros - good dimensional stability, clean, fAST set, tolerates moisture the best

cons - most rigid (STIFFER!), difficult to remove from mouth, poor tear strength, adheres to teeth

shortest working and set time (6-7 min)

use custom tray, more accurate in uniform thin layers 2-4 mm thick

235

zinc oxide eugenol is an impression paste

pros

cons

accelerated by adding water. to retard the set add inert oils

pros - record soft tissue at rest, sets in 5 min, stable

cons - messy, sticky, tiissue irritant, not elastic, hard to manipulate

SET HARD in mouth

a chemical rxn to form a CHELATE

236

gypsum

weaker in tensile strength than compressive strength
-all products are reacted with water to form calcium sulfate dehydrate

237

Type I gypsum - Plaster

rarely used

238

Type II gypsum - Plaster, Model

model or lab plaster
-make casts when strength isn't important (ortho)
-WEAKEST gypsum product

239

Type III gypsum - Dental stone

Class I Dental Stone
-high strength improved die stone

240

Type IV gypsum - Dental Stone, high strength

Class II Stone or improved stone
-for making stone "dies"

241

main constituent of dental plasters and stone is

calcium sulfate hemihydrate

dental stone (alpha)
dental plaster (beta) (plaster of paris)

242

dental stone v. plaster

main diff is particle size and shape
-plaster requires 2x more water, has higher setting expansion

243

when packing cord for a pt with HTN< use a cord impregnanted with

ALUM - aluminum potassium sulfate

zinc chloride is caustic and causes delayed healing